Problem: $9bc + 9bd + 5b + 1 = -10c + 4$ Solve for $b$.
Solution: Combine constant terms on the right. $9bc + 9bd + 5b + {1} = -10c + {4}$ $9bc + 9bd + 5b = -10c + {3}$ Notice that all the terms on the left-hand side of the equation have $b$ in them. $9{b}c + 9{b}d + 5{b} = -10c + 3$ Factor out the $b$ ${b} \cdot \left( 9c + 9d + 5 \right) = -10c + 3$ Isolate the $b$ $b \cdot \left( {9c + 9d + 5} \right) = -10c + 3$ $b = \dfrac{ -10c + 3 }{ {9c + 9d + 5} }$